1. Field of the Invention
The present invention relates to a high frequency current detecting apparatus for detecting a high frequency current flowing through a conductive material.
2. Description of the Related Art
A high frequency current is employed in various apparatuses, such as communication equipment, computer, or audio video equipment. In these apparatuses, as a result of flowing of the high frequency current, there is a possibility that an unnecessary electromagnetic wave is radiated to the outside. When such electromagnetic wave is radiated, there is a case where a bad influence is exerted on another equipment. Thus, it is necessary to take a suitable countermeasure against electromagnetic wave interference.
When the countermeasure against the electromagnetic wave interference is carried out, it becomes important to measure the intensity of the high frequency current which becomes the cause of generation of the electromagnetic wave. Besides, for example, also in the case where a product in which the countermeasure has been carried out is inspected, it is necessary to measure the high frequency current.
Conventionally, measurement of the high frequency current is carried out, for example, by cutting a circuit conductor formed on a printed circuit board and directly inserting an ammeter, or by inserting a low resistor to the cut portion and measuring a voltage at both ends thereof.
However, such conventional measurement of the high frequency current has problems as described below. That is, since the printed circuit board or the like is damaged due to cutting of the circuit conductor, it becomes difficult to maintain the reliability. Besides, a certain technique is necessary for the operation of cutting the circuit conductor, and it takes a labor and time. Moreover, since the ammeter or resistor is inserted to the cut circuit conductor, the intensity of current flowing through the circuit conductor is changed, or the frequency bandwidth is changed, so that it is difficult to carry out measurement with high precision. Besides, the operation of an apparatus is influenced by insertion of the ammeter or resistor, so that there is also a case where it is difficult to measure a current value in an original operating state of the apparatus.
An object of the present invention is therefore to provide a high frequency current detecting apparatus which can measure a high frequency current with high precision without cutting a circuit conductor.
The present invention relates to a high frequency current detecting apparatus made to achieve the foregoing object. That is, the detecting apparatus comprises a core having a hollow portion, a first conductive material inserted in the hollow portion of the core and having both ends respectively protruding from both ends of the hollow portion to form probe portions, a second conductive material electrically insulated from the first conductive material and inserted in the hollow portion of the core, a resistor for generating a voltage corresponding to a high frequency current flowing through the second conductive material while the first conductive material is made a primary coil and the second conductive material is made a secondary coil, and a shield provided around the core.
In the invention as described above, the two probe portions of the first conductive material are brought into contact with different two points on a circuit conductor of an object to be measured. By this, a part of high frequency current flowing through the circuit conductor is shunted to the first conductive material, and a magnetic field is generated in the core by this shunt current. As a result, an electromotive force is excited at the second conductive material, a current flows through the resistance, and a voltage corresponding to the intensity of the current is generated at both ends of the resistor. Besides, by the shield provided around the core, it is possible to prevent an electromagnetic field irrelevant to the measurement from entering the inside of the core, so that it becomes possible to carry out the measurement with high precision.